This invention relates to a method and product for preventing yarn tail breakage during yarn winding. The invention disclosed in this application has particular utility in the winding of yarn carriers, for example cylindrical or conical tubes, with yarn intended for knitting or weaving. Winding takes place in open-end spinning, twisting and other processes wherein yarn is wound onto the carriers. Yarn carriers used in these processes are wound with a trailing "tail" of yarn which the end of yarn on an exhausted carrier to be tied to the leading end of yarn on the succeeding full package. The tail is necessary if the transfer from the exhausted to a full package is to take place without dropping needles, which causes a serious defect in the knitted fabric.
While the invention disclosed in this application has utility on a number of different types of yarn carriers, for purposes of illustration the invention will be described with reference to a tubular textile yarn package which is formed of pressed paper and has a generally frusto-conical shape. While carriers come in various configurations, one common type of carrier is a cone which has an angle of taper of 5 degrees, 57 minutes.
As described above, this type of carrier must be wound with a tail in order for it to be considered a first quality package. An acceptable rate of yarn tail breakage is about one percent, with between two and three percent being average. Since knitters require yarn packages with yarn tails, yarn tail breakage is a serious problem both from the standpoint of yarn quality and from the standpoint of increased cost to the processor which results from backwinding defective packages, returns from customers, and the like.
The yarn tail is usually formed by taking a length of yarn and extending part of it over the open mouth of the large end of the carrier. The carrier is then applied to a cradle which has a carrier holder base plate which fits into the large end of the carrier and holds the yarn, and a carrier holder nose plate which secures the carrier for proper rotation about a fixed axis. The carrier is wound by surface drive against a rotating drum which feeds the yarn onto the rotating carrier in a predetermined pattern. This assembly is referred to generally herein as a "yarn carrier holder."
Until relatively recently, winders were designed so that the carrier holder base plate had an internal taper which corresponded to the taper of the carrier. This meant that for a fairly substantial distance on the order of 1/4 of an inch, the surface of the carrier holder base plate and the inner surface of the carrier were parallel with each other and in flush contact. The yarn trapped across the mouth of the carrier was thereby held firmly along the entire length of contact between the carrier and the base plate. This resulted in a secure grip while, at the same time, any stress applied to the yarn was spread over a relatively long distance.
Some winder manufacturers have designed cradles which have universal carrier holder base plates and nose plates. The plates are adapted to receive carriers having various angles of taper without the additional labor and lost operating time required to conform the cradle to the precise type of carrier being wound. While substantial efficiencies are achieved by this new type of winder, the angle of the portion of the base plate which fits into the large end of the carrier is no longer necessarily parallel to and flush with the inner surface of the carrier. Therefore, the yarn tail passes between the carrier and the base plate at two diametrically opposed edges rather than wide, flush surfaces. As long as there is little or no relative movement between the base plate and carrier, this fact is of little consequence. Therefore, when starting an empty carrier, there is often little difficulty since the carrier itself is very lightweight and has very little inertia.
Accordingly, the carrier begins rotation with the base plate and there is little or no relative movement which could cause the yarn to be pinched or cut. However, as yarn is wound onto the carrier, it increases substantially in weight and inertia. Many winders have automatic stop motions which utilize, for example, an air brake to very quickly stop the rotation of carrier when the package is full or when a break in the yarn occurs. The substantial inertia created by a full or near-full package is sufficient to cause the package to rotate relative to the base plate during stopping and starting. In the new types of winders described above, the edge of the base plate which presses against the yarn exerts a substantial amount of force and is more than sufficient to cut the yarn in two. As a result, the yarn package is no longer first quality and must either be rewound or sold as second quality.
Murata winders are widely used in the textile industry and present a unique, potential cause of yarn tail breaks. Murata winders include a rubber drive ring which sits on one end of the yarn carrier holder and, when the carrier is donned, sits against the adjacent end of the carrier. The drive ring contacts the driving surface of the drum during the initial winding phase and causes the carrier to rotate. When enough yarn has been built up on the carrier, the diameter of the carrier becomes greater than the diameter of the drive ring, and thus the carrier is thereafter rotated by direct contact between the carrier and the drum. It has been observed that the rubber ring will sometimes cut the yarn tail both during starting and stopping due to the contact between the rubber ring and the end edge of the carrier across which the yarn tail extends. The problem has become progressively worse as the winding speed of modern winders, open-end spinning machines, twisters, and the like have increased.
An earlier solution to this problem has been to make the yarn carriers slightly undersized so that the end of the carrier does not contact the rubber ring. However, this can cause misalignment problems and requires that the carrier manufacturer make a special carrier just for Murata winders. This increases the cost of the carrier and related inventory control costs to both the manufacturer and the yarn producer.
Applicant has reduced this problem to a significant extent by modifying the design of the carrier to incorporate grooves into the end of the carriers which protect the yarn by providing a slight recess in which the yarn at least partially resides thereby reducing the force on the yarn. This development is exemplified in applicant's prior U.S. Pat. No. 4,700,904.
The invention described in this application provides further improvement in yarn carrier quality easily, efficiently and inexpensively.